The deposition of particles by means of cold spraying processes, for example on turbine blades, has to date only been possible with particles larger than approximately 5 μm. This is due to the momentum transfer properties of the particles onto the surface. For various reasons, however, the use of cold spraying processes to spray nanoparticles is of interest.
In order to make this possible, it has been proposed to provide nanoparticles with shells in order to increase their size and mass with a view to achieving suitable momentum transfer properties. Particles which have a nanoparticle as the core and are surrounded by a shell or capsule are known, for example, from DE 101 31 173 A1, even if the core-shell particles described therein have dimensions of less than 1 μm.
As described, for example, in EP 1 548 134 A2, the nanoparticles may be produced by repeated fracture of microparticles during a milling process.
US 2005/0158723 A1 discloses irreversibly colloidal, i.e. finely distributed, chains with recognition sites. The aim of this is to provide a new type of tool for diagnosing and/or preparing an identification analysis or assay of species in a liquid sample.
The document illustrates the assembly of colloidal particles in the form of one or more chains, which are characterized in that they have an irreversible structure and have at least one recognition site for a species other than the ligands which are associated with the linear arrangement of the particles. In accordance with this document, the colloidal chains may have a relatively rigid, semirigid or flexible structure.